The project is designed to study the possible intrarenal actions of angiotensin II and the prostaglandin system, both of which may be involved in the control of intrarenal blood flow and tubular sodium handling. Using inhibitors of the renin angiotensin system and of prostaglandin synthesis changes in renal function and renal hemodynamics will be determined. The experiments will be carried out on dogs. Total renal blood flow will be determined using an electromagnetic flowmeter, and the clearance of inulin will be used as an estimate of glomerular filtration rate. Intrarenal blood flow distribution will be measured using radioactive microspheres. Sodium excretion will be calculated by standard techniques. The effects of various inhibitory drugs alone and in combination will be used to study the changes in the hemodynamic effects produced by the diuretic furosemide. Additional studies will be carried out in which renal secretion will be modified by the use of furosemide.